Goigen

Good day all, I would like to find out if anyone else has experienced the issue of a generator tripping the earth leakage after about 20 minutes of running? Using a 12,5kVA Turner Morris Industrial type generator which powers a house. Runs beautifully for plus minus 20 minutes, then trips the earth leakage in the DB board. Even dropping all the circuit breakers and just having the earth leakage on does not help and the earth leakage keeps tripping. The generator used to trip it's own 32A breaker before and it was replaced with a new 35A unit. I gathered this would be fine as even with a power factor of 0.8, it would still be able to make 45A comfortably and be covered by the 35A breaker? I doubt the AVR could be overcharging enough to trip a 60A earth leakage before the 35A breaker on the generator trips? What makes this so frustrating is that on normal council supply everything works hunky dory and nothing goes wrong...